Recent entries into the field of high performance resins and fibers include polyphenylene sulfides, polyetherimides, aromatic polyether-ether ketones (PEEK) and aromatic polyether-ketone-ketones (PEKK). This invention concerns a process for preparing aromatic polyether-ketone-ketones (PEKK). PEKK polymers are currently being made via a two step AlCl.sub.3 based Friedel-Craft reaction. Such a process requires virtually stoichiometric quantities of AlCl.sub.3 in both steps and also a recrystallization of the material to arrive at the desired isomer. The removal of excess AlCl.sub.3 by an extraction and a purification step requires the use of large, ususally expensive, corrosion resistant vessels and drying equipment.
The present invention provides an improvement over the above Friedel-Craft system as it is a one step method and does not require an extensive extraction procedure.
I. Fukawa et al., Macromolecules 24, 3838-3844 (1991) disclose a process for the preparation of aromatic poly(ether ketones) (PEK) by the reaction of an aromatic dihalide with sodium carbonate in the presence of high surface area solid silica catalyst with copper salt co-catalyst. Formation of a PEKK from 1,4-bis(4-fluorobenzoyl)benzene (identified as 4,4"-difluoroterephthalophenone) is reported. Fukawa reported that the reaction occurs on the internal surfaces of pores in the silica particles and on the external surfaces of the silica particles. The present invention presents an improvement over the Fukawa et al. process because the silicon based catalysts used in the present process are more easily separated from the polymer than are the silica particles used by Fukawa et al. For example, present catalysts may be separated by liquid extraction under non-alkaline conditions.
H. R. Kricheldorf and G. Bier, Polymer, 25, 1151-1156 (1984) disclose the preparation of poly(ether ketone)s and poly(ester ether ketone)s by the reaction of 4,4'-difluorobenzophenone with silylated bisphenols.
H. R. Kricheldorf and P. Jahnke, Makromol. Chem, 191, 2027-2035 (1990), disclose the preparation of poly(ether sulfone)s by the reaction of 4,4'-dichlorodiphenyl sulfone with silylated bisphenols.
H. R. Kricheldorf and P. Jahnke, Makromol. Chem., Rapid Commun. 12, 331-335 (1991), disclose the silicon catalyzed synthesis of poly(ether-sulfones) from 4,4'-dihalogenodiphenyl sulfones in the presence of potassium carbonate and N-methylpyrrolidone and N-phenylpyrrolidone solvent.
H. R. Kricheldorf, Makromol. Chem., Macroml. Symp., 54/55, 365-388 (1992), discloses various polymer synthetic methods that involve the polycondensation of silylated aromatic monomers.